The publishers of the News of the World suffered "collective amnesia" over the extent of illegal phone-tapping by its reporters, a group of MPs have said.
The Culture, Media and Sport committee interviewed News International bosses after the Guardian claimed the practice was widespread at the Sunday tabloid.
There had been more than a handful of victims and it was inconceivable no-one at the tabloid had known, the MPs said.
News International rejected the claims and said the committee had exaggerated.
In 2007, the News of the World's royal editor Clive Goodman and private investigator Glenn Mulcaire were jailed after admitting hacking into the phone messages of royal staff.
The paper said it was an isolated case but last year the Guardian reported that several public figures may also have had their messages hacked into by News of the World reporters.
The cross-party parliamentary committee criticised the Press Complaints Commission for not investigating the case properly and called for the watchdog to be given greater powers to help improve its credibility and authority.
During the committee's own investigation, MPs questioned executives from both newspapers - including Andy Coulson, who resigned as editor of the News of the World over the incident and is now Tory leader David Cameron's director of communications.
But in their report published on Wednesday the committee accused News International executives of "deliberate obfuscation".
The report said: "It is likely that the number of victims of illegal phone hacking will never be known, not least because of the silence of Clive Goodman and Glenn Mulcaire and the 'collective amnesia' at the newspaper group.
"The report notes however, that it is certainly more than a 'handful', cited by both the newspaper and the police."
The MPs concluded it was "inconceivable" that no one else at the News of the World knew what was going on, although they said they saw no evidence that Mr Coulson knew phone-hacking was taking place.
They said it was right that he had resigned from his post.
The MPs also said they were concerned about the "readiness of all of those involved: News International, the police and the PCC to leave Mr Goodman as the sole scapegoat without carrying out a full investigation at the time".
They added News International had not volunteered any details about any payoffs to either Goodman or Mulcaire but the committee was "left with a strong impression that silence has been bought".
In a briefing to reporters, committee member and Labour MP Tom Watson said: "Scotland Yard are sitting on a whole bank of information and data about very senior people in public life who were hacked..."
He said he hoped the information commissioner would investigate whether a change in the law was needed.
'Scrutiny and accountability'
But, in a statement, News International said the committee failed to provide any new evidence.
The company also accused "certain members" of the committee of following a party-political agenda and making "innuendo, unwarranted inference and exaggeration".
The Guardian welcomed the committee's findings and said: "The press has a proud record of shining a light into the darkest corners of our public institutions.
"As an industry we need to show we are willing to accept the same level of scrutiny and accountability."
Lady Buscombe, who chairs the PCC, said the organisation had investigated the claims as thoroughly as possible and rejected calls for it to be given investigative powers by the government.
"If you want a press, a free press that is not regulated by the state and therefore does not have pressure on it from politicians, you have to be very careful what you wish for," she said.
Commons culture committee chairman John Whittingdale said the affair did not prove the press was out of control.
"There is evidence things have improved. The jailing of a reporter was a profound shock to newspapers and now they are more careful about what they do and pay more attention to the PCC code," he said.